CODEWITHSUNDEEP
amazon-web-servicesamazon-cloudwatchmetrics
Ryan-Neal Mes
Ryan-Neal Mes

Reputation: 6263

How do I combine 2 search metrics with math expression in cloudwatch?

I am trying to get the percentage memory used when running a lambda to display in a graph on cloudwatch. I know there are other ways I can pull the data, but for reasons outside of the scope of this question, I would like to stick to using search to pull the metrics.

I have the following graph

{
    "metrics": [
        [ { "expression": "SEARCH('{SomeMetricNamespace} MetricName=\"MemorySize\"', 'Average', 300)", "id": "m1", "visible": "true" } ],
        [ { "expression": "SEARCH('{SomeMetricNamespace} MetricName=\"MaxMemoryUsed\"', 'Average', 300)", "id": "m2", "visible": "true" } ],
        [ { "expression": "m2/m1*100", "label": "pecentage memory used", "id": "e1", "stat": "Average" } ]
    ],
    "view": "timeSeries",
    "stacked": false,
    "region": "us-west-2",
    "stat": "Average",
    "period": 300,
    "title": "Memory",
    "yAxis": {
        "left": {
            "label": "Percentage Usage",
            "showUnits": false
        }
    },
    "liveData": false
}

The error I am getting

Error in expression e1 [Unsupported operand type(s) for /: '[Array[TimeSeries], Array[TimeSeries]]']

Is there a way to combine the first 2 expressions to give me the percentage memory used?

Upvotes: 8

Views: 14065

Answers (2)

Paula T
Paula T

Reputation: 1598

In case this helps someone else, I had a similar error from the expression:

Sum(m1, m2)

Turns out the fix was dead simple. Just had to add brackets to change the input to an array of time series, which is an accepted input type per the docs.

Sum([m1, m2])

Upvotes: 3

OARP
OARP

Reputation: 4077

The result of the expressions are arrays of time series so you can not apply directly operations (+ - * / ^). As a workaround you could transform each time series into single values (average values) for each expression and then calculate the percentage.

The source should be similar to this:

{
"metrics": [
    [ { "expression": "SEARCH('{SomeMetricNamespace} MetricName=\"MemorySize\"', 'Average', 300)", "id": "m1", "visible": "false" } ],
    [ { "expression": "SEARCH('{SomeMetricNamespace} MetricName=\"MaxMemoryUsed\"', 'Average', 300)", "id": "m2", "visible": "false" } ],
    [ { "expression": "AVG(m1)", "label": "AVGMemorySize", "id": "e1", "visible": "false" } ],
    [ { "expression": "AVG(m2)", "label": "AVGMaxMemoryUsed", "id": "e2", "visible": "false" } ],
    [ { "expression": "e2/e1*100", "label": "pecentage memory used", "id": "e3", "stat": "Average" } ]

    ],
    "view": "timeSeries",
    "stacked": false,
    "region": "us-west-2",
    "stat": "Average",
    "period": 300,
    "title": "Memory",
    "yAxis": {
        "left": {
            "label": "Percentage Usage",
            "showUnits": false
        }
    },
    "liveData": false
}

Upvotes: 2

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